The proposed research will continue an analysis of the properties of the system of cerebral neurons responsive to genital stimulation (genital sensory neurons) in the female cat, and extend the investigation to include the female rhesus monkey. Through the use of chronic single-unit recording methods, the activity of brainstem and diencephalic genital sensory neurons will be examined during the elicitation of behavioral responsesby vaginal stimulation in ovariectomized, anestrous and estrogen-treated cats. The objective is an identification of differences in the activity of these neurons in the estrous and anestrous conditions, and an elucidation of some of the neuronal processes controlling receptivity to genital stimuli in the cat. In most of these experiments, the genital stimulus will be deliverey manually, but in later stages of the research, activity of single genital sensory neurons will be recorded by telemetry during natural mating. Quantitative analysis of single unit activity and assessment of its relationship to behavioral events will be conducted by means of laboratory computers. Genital sensory mechanisms in the female rhesus monkey will be investigated in a series of acute experiments in which the brainstem and subcortical regions of the forebrain are mapped for single-unit responses to vaginal stimulation. All monkeys will have been ovariectomized and they will be either estrogen-treated or untreated in preparation for recording. The work on the monkey will provide a delineation of the basic organization and sensory properties of cerebral genital sensory neurons in this species. Collectively the findings from studies on the cat and monkey should contribute to an understanding of the mechanisms through which genital sensations influence the expression of mating behavior and the mode of action of gonadal hormones on genital sensory processes.